1. Field Of The Invention
The present invention relates generally to micro devices, and more particularly, but not exclusively, to micromechanical system structures and manufacturing methods.
2. Description Of The Background Art
A micro electromechanical system (MEMS) typically includes micromechanical structures that may be actuated using electrical signals. An example of a MEMS device is the Grating Light Valve(trademark) (GLV) device available from Silicon Light Machines, Inc. of Sunnyvale, Calif. GLV-type devices are described in the following disclosures, which are incorporated herein by reference in their entirety: U.S. Pat. No. 5,311,360 to Bloom et al,; U.S. Pat. No. 5,841,579 to Bloom et al.; and U.S. Pat. No. 5,661,592 to Bornstein et al.
Generally speaking, a GLV-type device is a light modulator. It may be used in various applications including video, printing, and optical switching, for example. A GLV-type device includes an array of moveable structures referred to as xe2x80x9cribbonsxe2x80x9d. A ribbon typically includes a metallic layer formed over a resilient, suspended structure. Under the ribbon is a bottom electrode that works in conjunction with the metallic layer, which serves as a top electrode. An air gap separates the bottom electrode from the metallic layer. Applying a voltage difference between the ribbon and the bottom electrode generates an electrostatic field that pulls the ribbon towards the bottom electrode. Light that impinges on the reflective metallic layer may thus be modulated by reflection or diffraction by controlling the applied voltage.
The response of a GLV-type device to a control signal, such as an applied voltage, is also referred to as its xe2x80x9cdriving characteristicxe2x80x9d. As can be appreciated from the foregoing, the better a device""s driving characteristic, the better it can modulate light. Thus, it is desirable to have GLV-type device that has a relatively stable driving characteristic.
In one embodiment, a micro device is formed by depositing a sacrificial layer over a metallic electrode, forming a moveable structure over the sacrificial layer, and then etching the sacrificial layer with a noble gas fluoride. Because the metallic electrode is comprised of a metallic material that also serves as an etch stop in the sacrificial layer etch, charge does not appreciably build up in the metallic electrode. This helps stabilize the driving characteristic of the moveable structure. In one embodiment, the moveable structure is a ribbon in a light modulator.
These and other features of the present invention will be readily apparent to persons of ordinary skill in the art upon reading the entirety of this disclosure, which includes the accompanying drawings and claims.